PURPOSE: To apply a decision analytic model to determine whether the addition of magnetic resonance (MR) lymphography to the diagnostic workup of patients with intermediate or high probability of lymph node metastases is cost effective from a health care perspective. MATERIALS AND METHODS: The data that were used for the decision analytic model were obtained from an empiric study population of 375 patients. As the input of the decision analytic model was made given prospective patient data from several hospitals, the ethics review board of each hospital approved the study. Written consent was obtained from all patients. To investigate possible differences between strategies that utilize MR lymphography and those that do not (pelvic lymph node dissection [PLND]), two outcome measures were examined and combined in an incremental cost-effectiveness ratio (ICER) of health care resources consumed and quality-adjusted life-years (QALYs). Probabilistic and one-way sensitivity analyses were performed. RESULTS: The PLND strategy is dominated by the MR lymphography strategy. Probabilistic sensitivity analysis showed that in 63% of simulations, MR lymphography was cost saving and resulted in better patient outcome for patients with prostate cancer and intermediate or high probability of lymph node metastases. The probability of MR lymphography being inferior (more expensive and worse patient outcome) is less than 3%. CONCLUSION: MR lymphography is an efficient strategy in the detection of lymph node metastases of prostate cancer when compared with the PLND strategy.